In service station environments, fuel is stored underneath the service station in underground storage tanks (USTs). The USTs typically hold thousands of gallons of fuel. In order to transfer fuel from the USTs to fuel dispensers above the ground in the service station forecourt so that the fuel can be dispensed to vehicles, a submersible turbine pump (STP) is provided. The STP comprises a turbine and motor that draws fuel from the UST. After the fuel leaves the STP, the fuel is distributed via a main fuel piping conduit through the service station. Individual fuel dispensers draw fuel from the main fuel piping conduit via a branch conduit that is fluidly coupled to the main fuel piping conduit. The fuel is then delivered into the fuel dispenser, metered and dispensed to a vehicle through a hose and nozzle combination.
Each of the individual fuel dispensers contains meters that measure the amount of fuel dispensed to a vehicle. Since this fuel originates from USTs, the amount of fuel dispensed out of the USTs is the combination of all of the metered fuel dispensed out of the individual fuel dispensers. The fuel dispenser meter data is communicated to a single site controller (SC) at the service station. The SC uses the individual fuel dispenser meter data to track the inventory levels of the USTs and to generate reports on this inventory. The SC may also provide fuel dispenser meter data information to a tank monitor (TM) system as is described in U.S. Pat. Nos. 5,665,895; 5,544,518; and 4,977,528, all of which are incorporated by reference in their entirety. The TM uses the fuel dispenser meter data as a reference point to calibrate the tank-strapping curve for the UST. A tank-strapping curve is a curve that correlates a liquid level in the UST to a volume level.
There are several factors that could cause the fuel dispenser meter data to not be an accurate account of the amount of fuel drawn out of the USTs and delivered to the fuel dispensers. First, a person could have tampered with the fuel dispenser meter and/or electronics such that the amount of fuel dispensed to a vehicle is different than measured by the fuel dispenser meter. In a typical fraud scenario, the fuel dispenser meter is tampered to measure more fuel than is actually dispensed so that customers get charged for more fuel than is dispensed. Second, the fuel dispenser meter may not be properly calibrated. This will cause the fuel dispenser meter to not accurately reflect the amount of fuel dispensed. Third, there may be a leak present in the fuel piping between the UST and the fuel dispenser meters, which will cause the amount of fuel drawn out of the UST to be less that the amount of fuel measured and delivered by the fuel dispenser.
If any of the aforementioned events occur, the fuel dispenser meter data that is collected by the SC will not be accurate as well. If the TM uses the fuel dispenser meter data from the SC for calibration of the tank-strapping curve, the tank strapping curve will be inaccurate as well. Further, this condition could go unnoticed for long periods of time.
Therefore, there exists a need to be able to confirm absolutely the amount of fuel drawn out of the USTs so that this amount can be compared to the fuel dispenser meter measurements to ensure that fraud, calibration, and/or leak issues are not present in the service station environment. Further, it may be important to base the tank-strapping curve calibration on another baseline of the amount of fuel drawn out of the UST rather than using the measurements of the individual fuel dispenser meters.